1. Field of the Invention
The present invention relates to a method for removing etching residue remaining after metal lines are formed by etching a metal film using a resist pattern as a mask, and the unnecessary resist patterns are removed in the metallization step of a semiconductor fabrication method. The present invention also relates to a semiconductor device fabrication method using this etching residue removal method.
2. Description of the Related Art
In the metallization step in the semiconductor device fabrication method, a metal film (e.g., aluminum film) is formed on a substrate via an insulation film, the resist film is coated thereon, and a resist pattern is formed by patterning the resist film by a photolithography technology. Then, metal lines are formed by metal-etching the metal film based on plasma dry etching using this resist pattern as a mask, and unnecessary resist patterns are removed (stripped) by ashing.
One method to remove unnecessary resist patterns when metal etching ends relies upon a stripper, such as thermal organic acid, and another method relies upon ashing.
The resist-pattern-removal method which uses ashing is easier than the resist-pattern-removal method which uses a stripper, but if the amount of impurities, such as metal, in the resist pattern is high, an etching residue remains even after resist patterns are removed, and this often adversely affects the semiconductor elements. Therefore etching residue is removed by performing a cleaning sequence after metal etching. In other words, the etching residue is removed by employing the etching residue removal method.
The conventional etching residue removal method includes a series of processing: a stripper processing for stripping the etching residue by an amine stripper (e.g., mixed solution of hydroxylamine and catechol: product name “SST-3”), a rinsing processing for rinsing the insulation film and metal lines thereon by a rinse solution (e.g., isopropyl alcohol of which a constituent is 2-propanol, hereafter called “IPA”), a washing processing for washing the insulation film and metal lines thereon by pure water, and a drying processing for drying the insulation film and the metal lines thereon.
One example of the conventional etching residue removal method is shown in FIG. 4 of the accompanying drawings. L stands for liter(s), MIN stands for minute(s) and SEC stands for second(s) in FIG. 4.
Device used: a batch spray device having a spray nozzle that sprays stripper etc. This device alone can perform stripper processing, rinsing processing, washing processing and drying processing for a plurality of wafers.
Stripper processing: delivery amount of the stripper from the spray nozzle is 15 liters/minute, 375 liters of amine stripper (product name is SST-3) is used, processing time is 15 minutes.
Rinsing processing: delivery amount of the rinse solution is 6 liters/minute, one litter of rinse solution (IPA) is used, processing time is 10 seconds.
Washing processing: pure water is used, processing time is 4 minutes and 30 seconds.
Drying processing: processing time is 3 minutes.
Total processing time: 22 minutes and 40 seconds.
Another conventional etching residue removal method related to this method is disclosed in FIG. 8 of Japanese Patent Application Kokai (Laid-Open) No. 2002-158206. The etching residue removal method of this JP 2002-158206 A1 performs a cleaning sequence at least twice. The cleaning sequence includes the stripper processing for stripping the etching residue on the substrate by fluorine stripper, rinsing processing for rinsing the substrate with a rinse solution (mixed solution of IPA and water), washing processing for washing the substrate, and drying processing for drying the substrate. This cleaning sequence is continuously repeated at least twice.
An example of the etching residue removal method of JP 2002-158206 A1 is described below.
Device used: dip device to soak a substrate into a processing bath, or a spray device. This device alone can perform stripper processing, rinsing processing and washing processing. For drying processing, a dryer device is used.
Stripper processing: fluorine stripper (ammonium fluoride) is used, processing time is 3 minutes and 20 seconds.
Rinsing processing: rinse solution is a mixed solution of IPA and water (volume ratio 4:1), processing time is 2 minutes and 20 seconds.
Washing processing: pure water is used, processing time is 2 minutes and 20 seconds.
Drying processing: temperature is 23° C., dried in a nitrogen atmosphere, processing time is 7 minutes and 15 seconds.
Time for one cleaning sequence: 15 minutes and 15 seconds.
Total processing time: if performed twice, processing time is 30 minutes and 30 seconds (=15 minutes and 15 seconds×2).